Polyphase networks have been developed in conjunction with polyphase modulators for the generation of single sideband signals. U.S. Pat. No. 3,559,042 by Michael John Gingell issued Jan. 26, 1971 and entitled: "Polyphase Symmetrical Network" describes such a network. Application of these networks to single sideband modulators is described in an article also by Gingell entitled: "Single Sideband Modulation Using Sequence Asymmetric Polyphase Networks" Electrical Communication, Vol. 48 No. 1 and 2, pp 21-25, 1973. Utilizing digital signals to modulate or demodulate the analog input signal provides a practical analog modulator which is particularly adapted for use in frequency division multiplex transmission of telephone signals on carrier systems.
Utilizing a single polyphase network results in one having a notch at only one single frequency. However, as pointed out in both the article and patent by Gingell, by cascading "n" number of sections, having different notch frequencies .omega..sub.1, .omega..sub.2 --.omega..sub.n, a band of "n" different notch frequencies can be obtained. Utilizing the minimum number of cascaded sections to achieve the desired rejection band may result in a network which has an unacceptably high ripple in the passband. Such a network can be improved upon by adding still further cascaded sections which are so designed to reduce this passband ripple. However, such a solution is relatively expensive in terms of additional components.